Astronomers urged to consider more types of stars in search for extraterrestrial life

Researches urge astronomers not to limit search for extraterrestrial life to just Sun-type stars but consider larger and hotter ones. Pictured here is an artist's impression shows sunrise over CoRoT-7b, the smallest-known exoplanet.(Photo : NASA Goddard | European Southern Observatory)

Astronomers have an "attention gap" when it comes to considering what kind of stars to examine in the search for habitable planets, a University of Texas at Arlington physicist says.

"They've typically focused on less massive stars similar to our sun, classified as a G-type star, but should consider larger stars," physicist Martin Cuntz said.

Stars are given a letter classification based on criteria such as surface temperature, mass, luminosity and how common they are in the universe.

F-type stars are larger, more massive and hotter than our sun, and they exhibit increased ultraviolet radiation most astronomers believe would make the presence of extraterrestrial life on any orbiting planets unlikely.

Martin Cuntz said he believes they shouldn't be disregarded out of hand.

"F-type stars are not hopeless," Cuntz said. "There is a gap in attention from the scientific community when it comes to knowledge about F-type stars, and that is what our research is working to fill. It appears they may indeed be a good place to look for habitable planets."

The researchers examined the potential for extraterrestrial life in an environment of higher ultraviolet radiation, using DNA as an example of carbon-based macromolecules necessary for life and comparing estimates of DNA damage on planets in F-type star systems to the damage done on Earth by the Sun.

In considering several different types of F-type stars at different points in their evolution, they found, in some cases, the damage estimates were similar to the damage on Earth.

Cuntz and UT Arlington doctoral student Satoko Sato argue that since F-type stars have a wider habitability zone, where conditions could allow Earth-type planets to develop and sustain life, they warrant additional consideration.

"Our study is a further contribution toward the exploration of the exobiological suitability of stars hotter and, by implication, more massive than the Sun ... at least in the outer portions of F-star habitable zones, UV radiation should not be viewed as an insurmountable hindrance to the existence and evolution of life," Cuntz and Sato said.

Their study has been published in the International Journal of Astrobiology.

Cuntz and Sato suggest further research be undertaken to examine chemical models of planetary atmospheres in specific star-planet systems, including cases of F-type stars that are members of binary or higher-order systems.